The principal objective of this research is to further elucidate the contribution of platelets and platelet membranes to the thrombotic, hemostatic and coagulation processes. Stimulated platelets participate in these events in a dynamic fashion, which suggests that they are membrane-related events. Characterization of membrane enzyme activities, such as phospholipase A2 and the newly discovered superoxide-generating and reducing properties of human platelets, should serve to further enhance our knowlege of the biological properties of human platelets and platelet membranes. Methodology developed in this laboratory over the last several years for the isolation and biochemical characterization of platelet membranes and granules will be employed in these studies. Activity of phospholipase A2 is one of the signs of a 'stimulated' platelet and sets off a series of events which appear to be important in the cleavage and transformation of arachidonic acid, as well as subsequent effects on the platelet and platelet environment. Generation of superoxide radicals by platelets and platelet concentrates can have important implications for the supply and management of platelet concentrates for therapeutic purposes. Methods will be explored for inhibiting and/or scavenging free radicals which are formed in the supernatant of platelet concentrates. The clinical and economic consequences of such inhibition present an exciting challenge to develop this line of research.